How to avoid "kotlin.Any" type when generating code with openapi generator?

Issue

I've been learning recently about openapi generator and I wanted to generate a simple api using it, but after setting everything up and running the generator, it works mostly fine but all the types for my functions, entities and more are of type "kotlin.Any"

I am using Maven and this is the configuration for my plugin

<plugin>
                <groupId>org.openapitools</groupId>
                <artifactId>openapi-generator-maven-plugin</artifactId>
                <!-- RELEASE_VERSION -->
                <version>6.6.0</version>
                <!-- /RELEASE_VERSION -->
                <executions>
                    <execution>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>${project.basedir}/src/main/resources/openapi.yaml</inputSpec>
                            <generatorName>kotlin-spring</generatorName>
                            <configOptions>
                                <sourceFolder>src/gen/kotlin/main</sourceFolder>
                                <interfaceOnly>true</interfaceOnly>
                                <useSpringBoot3>true</useSpringBoot3>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

this is my autogenerated /users endpoint:

@Operation(
        summary = "Get user information",
        operationId = "usersGet",
        description = """This endpoint requires a valid bearer token""",
        responses = [
            ApiResponse(responseCode = "200", description = "OK", content = [Content(schema = Schema(implementation = kotlin.Any::class))]),
            ApiResponse(responseCode = "401", description = "")
        ],
        security = [ SecurityRequirement(name = "BearerAuth") ]
    )
    @RequestMapping(
            method = [RequestMethod.GET],
            value = ["/users"],
            produces = ["application/json"]
    )
    fun usersGet(): ResponseEntity<kotlin.Any> {
        return ResponseEntity(HttpStatus.NOT_IMPLEMENTED)
    }

this is how I declared my /users endpoing inside my .yaml file:

  /users:
    get:
      summary: Get user information
      description: This endpoint requires a valid bearer token
      security:
        - BearerAuth: []
      responses:
        "200":
          description: OK
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/UserResponse'
        "401":
          $ref: '#/components/responses/Unauthorized'
      tags:
        - user

and this is the model for UserResponse:

    UserResponse:
      example:
        lastName: Doe
        name: Jhon
        id: 1
        email: [email protected]
        token: fkljasdhf9fjkfh23fhkhiafo9
      properties:
        id:
          description: "Auto generated by the api, not required for any transaction"
          example: 1
          type: integer
        email:
          example: [email protected]
          type: string
        name:
          example: Jhon
          type: string
        lastName:
          example: Doe
          type: string
        token:
          description: Auto generated by the api once you create a user or login with
            valid credentials
          example: fkljasdhf9fjkfh23fhkhiafo9
          type: string

Is there something I am missing?

Solution

After some research, it looks like this problem is caused by the version of openapi generator. In my case I was using version 6.6.0 which seems to have a bug that provokes none of the classes to have the correct types. After updating to the latest current version (7.2.0) it works perfectly fine.

Answered By - Lordkaito